Commonly-owned U.S. Pat. No. 4,463,729 (Bullis et al, 1984) discloses a start of combustion (SOC) sensor that provides a SOC signal indicative of the onset of combustion event. The SOC sensor is an optical device disposed in the combustion chamber.
The SOC signal is advantageously supplied to a timing control circuit which delivers a timing control signal to a fuel delivery device, such as the controller associated with a fuel pump. The control circuit stores one or more start of combustion values which indicate the desired timing, relative to an engine cycle, for the start of combustion event as a function of speed and load. One or more adjustment signals are stored and applied as a function of speed and load to adjust the desired signal such that the control signal is corrected for delays. The actual SOC signal is compared with the desired signal to generate an error signal which may be used to finely adjust the stored SOC signal for particular speed and load conditions. This patent is incorporated by reference herein.